Flow-regulating expansion valve

ABSTRACT

To provide a small-sized solenoid-driven flow-regulating expansion valve which can be realized at low cost. In a flow-regulating expansion valve according to the present invention, a pipe forming a body thereof not only accommodates internal structures, such as a flow-regulating mechanism, a movable core, and a fixed core, but also serves as a part of piping of a refrigeration cycle. Further, a solenoid section including a solenoid coil is disposed outside the pipe in a manner surrounding the same. Therefore, substantial integration of the flow-regulating mechanism in the piping of the refrigeration cycle can be achieved, which makes the entire flow-regulating expansion valve very simple in construction. As a result, reduction of the size of the flow-regulating expansion valve and resultant reduction of material costs and manufacturing costs can be achieved, which makes it possible to achieve low costs of the flow-regulating expansion valve.

CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY

This application claims priority of Japanese Application No.2003-320006 filed on Sep. 11, 2003 and entitled “FLOW-REGULATING EXPANSION VALVE”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a flow-regulating expansion valve provided in a passage of refrigerant circulating through a refrigeration cycle, for decompressing refrigerant flowing in from an upstream side thereof by adiabatically expanding the refrigerant, and delivering the refrigerant at a constant flow rate, according to an amount of an electric current supplied thereto.

(2) Description of the Related Art

Conventionally, a flow-regulating expansion valve for use in a refrigeration cycle of an automotive air conditioner has been proposed which is capable of not only decompressing refrigerant flowing in from an upstream side thereof by adiabatically expanding the refrigerant, but also electrically controlling the flow rate of refrigerant to be delivered in the downstream direction (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2001-153495).

A flow-regulating expansion valve of the above-mentioned kind is formed by integrating a flow-regulating mechanism into a body block formed separately from piping constituting a refrigerant passage of a refrigeration cycle, and has a high-pressure refrigerant inlet passage for introducing high-pressure refrigerant and an expanded refrigerant outlet passage for delivering decompressed refrigerant toward an evaporator disposed downstream of the expansion valve. The preset differential pressure across the expansion valve as a differential pressure control valve is controlled by a solenoid, whereby the flow rate of refrigerant flowing through the expansion valve is held at a predetermined constant level corresponding to a differential pressure set by a solenoid.

However, this arrangement causes an increase in the size of the entire flow-regulating expansion valve because the body block is formed separately from the piping of the refrigeration cycle, and further, an internal refrigerant passage where internal structures of the flow-regulating mechanism, such as a restriction and a valve element, are arranged, and a solenoid section for drivingly controlling the internal structures are disposed in the body block separately from each other. Further, it is necessary to perform not only complicated adjustment for positioning the high-pressure refrigerant inlet passage, the expanded refrigerant outlet passage, and the internal refrigerant passage connecting these, according to the construction of the flow-regulating mechanism within the body block, but also resultant adjustment of the position of joint to the piping of the refrigeration cycle, which causes a considerable increase in the manufacturing costs of the expansion valve.

SUMMARY OF THE INVENTION

The present invention has been made in view of these points, and an object thereof is to provide a flow-regulating expansion valve which is compact in size and realized at low cost.

To solve the above problem, the present invention provides a flow-regulating expansion valve provided in a flow passage of refrigerant circulating through a refrigeration cycle, for decompressing refrigerant flowing in from an upstream side thereof by adiabatically expanding the refrigerant, and delivering the refrigerant at a constant flow rate set by a value of an electric current supplied to a solenoid coil, the flow-regulating expansion valve comprising a pipe forming a part of the refrigerant flow passage, a fixed core in the form of a hollow cylinder fixed in the pipe, a movable core in the form of a hollow cylinder disposed in the pipe in a manner opposed to the fixed core in an axial direction such that the movable core is movable in the axial direction, the solenoid coil circumferentially disposed outside the pipe in a manner surrounding the pipe, for generating a magnetic circuit including the movable core and the fixed core by an electric current which is externally supplied, to generate a solenoid force a magnitude of which corresponds to a value of the supplied electric current to thereby move the movable core to a predetermined reference position with respect to the fixed core, and a flow-regulating mechanism provided in the pipe, for performing valve-opening or valve-closing operation while moving the movable core to and from the predetermined reference position to adjust an internal passage cross-section, and delivering the refrigerant downstream at the constant flow rate.

The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a flow-regulating expansion valve according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the flow-regulating expansion valve according to the first embodiment of the present invention.

FIG. 3 is an explanatory view showing flow rate characteristics of the flow-regulating expansion valve according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a flow-regulating expansion valve according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of the flow-regulating expansion valve according to the second embodiment of the present invention.

FIG. 6 is an explanatory view showing flow rate characteristics of the flow-regulating expansion valve according to the second embodiment of the present invention.

FIG. 7 is a cross-sectional view of a flow-regulating expansion valve according to a variation of the second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a flow-regulating expansion valve according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view of the flow-regulating expansion valve according to the third embodiment of the present invention.

FIG. 10 is a cross-sectional view of a flow-regulating expansion valve according to a fourth embodiment of the present invention.

FIG. 11 is a cross-sectional view of the flow-regulating expansion valve according to the fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view of a flow-regulating expansion valve according to a variation of the fourth embodiment of the present invention.

FIG. 13 is a cross-sectional view of a flow-regulating expansion valve according to a fifth embodiment of the present invention.

FIG. 14 is a cross-sectional view of the flow-regulating expansion valve according to the fifth embodiment of the present invention.

FIG. 15 is a cross-sectional view of a flow-regulating expansion valve according to a sixth embodiment of the present invention.

FIG. 16 is a cross-sectional view of the flow-regulating expansion valve according to the sixth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]

First of all, a description will be given of a first embodiment of the present invention. FIG. 1 is a cross-sectional view of a flow-regulating expansion valve of the present embodiment. In the following description, an upper side and a lower side as viewed in the figure will be also referred to as the upstream side and the downstream side, respectively, with reference to the direction of flow of refrigerant.

As shown in FIG. 1, the flow-regulating expansion valve 1 comprises a body formed by a pipe 2 in the form of a hollow cylinder having opposite open ends, a fixed core 3, a movable core 4, a hollow member 5, and a valve element 6, accommodated in the pipe 2, and a solenoid section 10 disposed on the outer periphery of the pipe 2 in a manner surrounding the same.

Piping joints 70 having a generally oval shape are attached to respective opposite ends of the pipe 2. Each of the ends of the pipe 2 is formed with a contracted part, and the diameter of the contracted part is expanded after the piping joint 70 having been fitted on the pipe 2, so as to prevent the piping joint 70 from falling off. Further, the piping joint 70 is formed with a through hole 70 a through which a bolt extends, at a location outward of the pipe 2.

To connect the flow-regulating expansion valve 1 to the piping of a refrigeration cycle, not shown, piping joints identical in structure to the piping joint 70 are fitted on opposed pipes of the piping of the refrigeration cycle, and each pair of associated piping joints are faced to each other via an O ring, and then fixed to each other by inserting a bolt through the through holes of the two piping joints and tightening a nut. When the flow-regulating expansion valve 1 is connected to the refrigeration cycle, the pipe 2 forms a part of a refrigerant passage.

The fixed core 3 has a body in the form of a hollow cylinder, which has a fitting groove 31 circumferentially formed in an outer peripheral surface thereof at the center in the axial direction, and a downstream end of the fixed core 3 has an inner diameter increased by a predetermined amount to form a chamber 32 for housing a spring 81, referred to hereinafter. Further, the rim of an opening in an upstream end of the fixed core 3 forms a valve seat 33 on which the valve element 6 is seated. The fixing of the fixed core 3 in the pipe 2 is attained by receiving the fixed core 3 in the pipe 2, and then swaging a portion of the pipe 2 corresponding to the fitting groove 31 from the outside to fit the same in the fitting groove 31.

Further, on an upstream end face of the fixed core 3, there is mounted a hollow shaft 7 in the form of a bottomed and stepped hollow cylinder, which is closed on the upstream side. The hollow shaft 7 has an expanded part 71 in a downstream end thereof. The hollow shaft 7 is mounted on the fixed core 3 such that an extreme end of the expanded part 71 surrounds the upstream-side opening of the fixed core 3, and disposed such that the hollow shaft 7 communicates with a refrigerant passage, described hereinafter, formed by the hollow member 5. Further, the expanded part 71 has a predetermined opening 72 through a side surface thereof, for introducing refrigerant flowing from the upstream side.

The movable core 4 has a body in the form of a hollow cylinder, and is disposed in the pipe 2 at a location downstream of the fixed core 3. The movable core 4 can axially slide along the inner wall of the pipe 2 toward and away from the fixed core 3. An upstream end of the movable core 4 has an inner diameter increased by a predetermined amount to form a chamber 41 for housing the spring 81, referred to hereinafter. More specifically, the spring 81 (elastic member) is interposed between the fixed core 3 and the movable core 4 such that it extends through the chamber 32 in the fixed core 3 and the chamber 41 in the movable core 4, with opposite ends thereof fixed to the fixed core 3 and the movable core 4, respectively, whereby when the solenoid section 10 is not energized, the movable core 4 is supported by the fixed core 3 with a predetermined space therebetween.

The hollow member 5 has a body in the form of a hollow cylinder, with a downstream part thereof inserted in the movable core 4 and rigidly fitted therein and an upstream part thereof slidably fitted in the fixed core 3. The hollow member 5 has an upstream end thereof restricted to form an orifice 51 (restriction) having a fixed passage cross-section. Further, the hollow member 5 has three cylindrical support portions 52 extending upward from an upstream end face thereof in a manner arranged at circumferential intervals of 120 degrees, for supporting a valve portion, described hereinafter, of the valve element 6. It should be noted that in FIG. 1, only one of the three cylindrical support portions 52 is shown for convenience of description. Further, the hollow member 5 has a through hole 53 formed in a side wall thereof at the center in the axial direction so that a refrigerant pressure generated by driving the movable core 4 in an area defined by the fixed core 3, the movable core 4, and the hollow member 5 can be released into the internal refrigerant passage via the through hole 53.

The valve element 6 has a body in the form of a hollow cylinder, and comprises a guide portion 61 hermetically guided by the hollow shaft 7, and a valve portion 62 provided on the downstream side of the guide portion 61 in a manner continuous therewith such that the valve portion 62 can be seated on the valve seat 33. The valve portion 62 has an outer diameter larger than that of the guide portion 61, and is formed to have a tapered shape the diameter of which progressively decreases toward the downstream end thereof. Further, a communication hole 63 having a smaller diameter than the inner diameter of the guide portion 61 is axially formed through the center of the valve portion 62, for communication between the inside of the guide portion 61 and that of the hollow shaft 7. Furthermore, the hollow shaft 7 contains a spring 82 axially extending therein, and the downstream end of the spring 82 is held in contact with the upstream end face of the valve portion 62, for urging the valve element 6 in the downstream direction so as to constantly hold the downstream end face of the valve portion 62 in contact with the upstream end faces of the support portions 52 of the hollow member 5.

The solenoid section 10 is formed to have a generally hollow cylindrical shape, and disposed in a manner surrounding the pipe 2 from the outside. More specifically, a first bobbin 12 having a solenoid coil 11 wound therearound is disposed around the outer periphery of the pipe 2, and on the upstream end of the first bobbin 12, there is disposed a second bobbin 13 which cooperates with the first bobbin 12 to form a passage for a lead wire to a terminal of the solenoid coil 11. The first bobbin 12 and the second bobbin 13 are enclosed by a first yoke 14, and the upstream end of the first yoke 14 is closed by a second yoke 15, whereby a continuous magnetic circuit is formed.

In the flow-regulating expansion valve 1, the fixed core 3, the movable core 4, the first yoke 14, and the second yoke 15 form the magnetic circuit including the solenoid coil 11.

Next, a description will be given of the operation of the flow-regulating expansion valve 1. FIG. 1 shows the flow-regulating expansion valve 1 in a state of the solenoid coil 11 being deenergized, while FIG. 2 shows the same in a state of the solenoid coil 11 being energized.

First, in a state of no electric current being supplied to the solenoid coil 11, no attractive force is generated between the movable core 4, which is supported by the spring 81, and the fixed core 3, and hence, as shown in FIG. 1, the valve element 6 is seated on the valve seat 33 to hold the flow-regulating expansion valve 1 in a fully-closed state.

Then, when an electric current i is supplied to the solenoid coil 11, a solenoid force the magnitude of which corresponds to the value of the electric current i is generated, whereby the movable core 4 is attracted toward the fixed core 3, as shown in FIG. 2. As a result, a force is generated for moving the valve element 6 upward via the hollow member 5 against the urging forces of the springs 81 and 82. Consequently, the valve element 6 is held in a position where the solenoid force and the loads of the springs 81 and 82 are balanced with each other, whereby a predetermined passage cross-section is formed between the valve element 6 and the valve seat 33.

When a high-pressure refrigerant is introduced from the upstream side in the above-described state, the refrigerant is guided through the opening 72 of the hollow shaft 7, a refrigerant passage 65 between the valve element 6 and the valve seat 33, and gaps between the adjacent pairs of support portions 52 into an intermediate area 55 located immediately upstream of the upstream-side opening of the hollow member 5. Then, the refrigerant is adiabatically expanded while passing through the orifice 51, and flows downstream.

The refrigerant introduced into the intermediate area 55 is also introduced through the communication hole 63 into an inner area 75 formed between the valve element 6 and the hollow shaft 7. For this reason, the pressure of the refrigerant in the intermediate area 55 and that in the inner area 75 become equal to each other, whereby refrigerant pressure applied to the valve element 6 is canceled. Therefore, the hollow member 5 receives only the load of the spring 82 from the valve element 6.

Now, let it be assumed that the pressure of the refrigerant introduced into a refrigerant inlet 21 is represented by P1, the pressure of the refrigerant in the intermediate area 55, which has been reduced due to passage of the refrigerant through the refrigerant passage 65, by P2, the pressure of the refrigerant in a refrigerant outlet 22, which has been further reduced due to passage of the refrigerant through the orifice 51, by P3, the effective pressure-receiving area of the valve portion 62 in the seated state (i.e. the passage cross-sectional area of the inner area 55) by A, and the passage cross-sectional area of the orifice 51 by C. Then, a flow rate Gf of the refrigerant flowing through the flow-regulating expansion valve is represented by the following equation: Gf=KC(P2−P3)  (1)

-   -   where K represents a flow coefficient of the refrigerant.

On the other hand, insofar as the forces acting on the hollow member 5 are concerned, assuming that the solenoid force generated by the electric current i is represented by f(i), and the sum of the forces of the springs 81 and 82, which act in the downstream direction, is represented by fs, the relationship between the forces acting on the hollow member 5 in the upstream and downstream directions is represented by the following equation: (A−C)(P2−P3)=f(i)fs  (2)

From the equations (1) and (2), the flow rate Gf of the refrigerant is represented by the following equation: Gf=(KC/(A−C))(f(i)fs)  (3)

In the right side of the equation (3), the parameters except the solenoid force f(i) are substantially fixed values, and therefore the flow rate Gf is held at a constant value proportional to the electric current i supplied to the solenoid coil 11.

Next, the operation of the flow-regulating expansion valve 1 will be described based on a flow rate characteristic shown in FIG. 3. In FIG. 3, the abscissa represents the value of the electric current i supplied to the solenoid coil 11, and the ordinate represents the flow rate Gf of refrigerant flowing through the flow-regulating expansion valve 1. When the electric current i supplied to the solenoid coil 11 is equal to zero, the valve element 6 is seated on the valve seat 33 due to the load fs of the springs to hold the flow-regulating expansion valve 1 in a fully-closed state, and hence the flow rate Gf is also equal to zero.

When a current i of e.g. 0.3 A is supplied to the solenoid coil 11, and a solenoid force f(i) larger than the load fs of the springs is applied to the hollow member 5, the valve element 6 is immediately moved from the seated position to the position where the solenoid force f(i) and the load fs of the springs are balanced with each other, and is stopped there. Since the valve element 6 is moved away from the valve seat 33, refrigerant starts to flow. When the refrigerant flows, a differential pressure (P2−P3) is generated across the orifice 51.

At this time, when a refrigerant flow rate on the upstream side of the refrigeration cycle is increased to raise the pressure P1 in the refrigerant inlet 21, the valve element 6 is moved in a valve-closing direction for reducing the effective pressure-receiving area to restrict the refrigerant flow rate, thereby holding the differential pressure (P2−P3) across the orifice 51 at a constant level. On the other hand, when the refrigerant flow rate on the upstream side of the refrigeration cycle is reduced to lower the pressure P1 in the refrigerant inlet 21, the valve element 6 is moved in a valve-opening direction for increasing the effective pressure-receiving area to increase the refrigerant flow rate, thereby holding the differential pressure (P2−P3) across the orifice 51 at the constant level. As a result, the differential pressure (P2−P3) across the orifice 51 is constantly controlled to a constant value determined according to the electric current i. Consequently, as is apparent from the equation (1), the flow-regulating expansion valve 1 is capable of allowing refrigerant to flow at a constant flow rate dependent on the electric current i supplied to the solenoid coil 11.

As described above, in the flow-regulating expansion valve 1 of the present embodiment, the pipe 2 forming the body of the valve 1 not only accommodates the internal structures including the flow-regulating mechanism, the movable core 4, and the fixed core 3, but also serves as a part of piping of the refrigeration cycle. Further, the solenoid section 10 including the solenoid coil 11 is disposed in a manner surrounding the pipe 2 from the outside. Therefore, substantial integration of the flow-regulating mechanism in the piping of the refrigeration cycle can be achieved, which makes it possible to make the flow-regulating expansion valve 1 very simple in construction. As a result, reduction of the size of the flow-regulating expansion valve 1 and resultant reduction of material costs and manufacturing costs can be achieved, which makes it possible to achieve low costs of the flow-regulating expansion valve 1.

[Second Embodiment]

Next, a description will be given of a second embodiment of the present invention. FIG. 4 is a cross-sectional view of a flow-regulating expansion valve according to the present embodiment. It should be noted that component elements identical to those in the first embodiment are designated by identical reference numerals on an as-needed basis, and detailed description thereof is omitted.

As shown in FIG. 4, the flow-regulating expansion valve 201 has a pipe 202 in the form of a hollow cylinder accommodating a fixed core 203, a movable core 204, and a solid shaft 205, with a solenoid section 10 disposed on the outer periphery of the pipe 202 in a manner surrounding the same.

The pipe 202 in the form of a hollow cylinder has opposite ends thereof increased in diameter, and piping joints 70 are fitted thereon, respectively.

The fixed core 203 has a body in the form of a hollow cylinder having a fitting groove 31 circumferentially formed in an outer peripheral surface thereof, with a bottomed cylindrical stopper 251 fitted in a downstream end thereof, for supporting a spring 281, referred to hereinafter, and the solid shaft 205 from below. The stopper 251 has an upstream-side bottom thereof formed therethrough with a communication hole 251 a forming a part of a refrigerant passage through the flow-regulating expansion valve 201. Further, the rim of an opening in an upstream end of the fixed core 203 forms a valve seat 233.

The movable core 204 has a body in the form of a stepped hollow cylinder the inner diameter of which is increased at an upstream end thereof, and is disposed in the pipe 202 at a location upstream of the fixed core 203. The movable core 204 has a downstream end formed to have a tapered shape the outer diameter of which progressively decreases downstream, and the tapered downstream end forms a valve portion 241 which can be seated on the valve seat 233. The movable core 204 has a small-bore part 242 and a large-bore part 243 upstream of the small-bore part 242, and the solid shaft 205 is inserted in these parts 242 and 243. Between the movable core 204 and the inner wall of the pipe 202, there is formed a refrigerant passage 263 which allows passage of refrigerant introduced from the upstream side. Further, a non-magnetic member 207 in the form of a hollow cylinder formed in a manner continuous with the movable core 204 extends downstream from the extreme end of the valve portion 241 of the movable core 204.

The non-magnetic member 207, which is inserted into the fixed core 203, has a downstream end thereof circumferentially formed with a flange 271 extending radially outward to form a restriction 261 between the non-magnetic member 207 and the inner wall of the fixed core 203. Further, the non-magnetic member 207 has a side wall thereof formed with a predetermined through hole 272, for introducing into the inside of the member 207 part of refrigerant in an intermediate area 264 defined between the non-magnetic member 207 and the fixed core 203.

The spring 281 (elastic member) is interposed between the downstream end face of the non-magnetic member 207 and the upstream end face of the stopper 251, for urging the movable core 204 in the upstream direction, i.e. in the valve-opening direction via the non-magnetic member 207, so that when the solenoid section 10 is not energized, the movable core 204 is supported by the fixed core 203 with a predetermined space therebetween.

The solid shaft 205 is in the form of a stepped column, and the lower end of a small-diameter part 252 thereof is fixed to the upstream end face of the stopper 251. The small-diameter part 252 has the movable core 204 and the non-magnetic member 207 fitted thereon to guide them in the directions of motion thereof. Further, a large-diameter part 253 formed in the upstream end of the solid shaft 205 not only guides the large-bore part 243 of the movable core 204, but also defines a predetermined inner space 262 between the junction (stepped portion) of the small-diameter part 252 and the large-diameter part 253, and the movable core 204.

Further, a polyimide film 291 (sealing member) is provided on the upstream end face of the movable core 204 and the upstream end face of the solid shaft 205 in a manner hermetically covering these, thereby preventing refrigerant within the inner space 262 from flowing out upstream through a gap between the large-diameter part 253 and the inner wall of the movable core 204.

Next, a description will be given of the operation of the flow-regulating expansion valve 201. FIG. 5 shows the open state of the flow-regulating expansion valve 201, while FIG. 4 shows the fully-closed state of the same.

First, in a state of no electric current being supplied to the solenoid coil 11, the movable core 204 is urged upstream by the spring 281, and hence, as shown in FIG. 5, the valve portion 241 is held away from the valve seat 233 to hold the flow-regulating expansion valve 201 in its open state.

Then, when an electric current i is supplied to the solenoid coil 11, a solenoid force the magnitude of which corresponds to the value of the electric current i is generated, whereby the movable core 204 is attracted toward the fixed core 203. As a result, a force acting in the direction of seating the valve portion 241 of the movable core 204 against the urging force of the spring 281 is generated. Consequently, the valve portion 241 is held in a position where the solenoid force and the load of the spring 281 are balanced with each other, whereby a predetermined passage cross-section is formed between the valve portion 241 and the valve seat 233.

When a high-pressure refrigerant is introduced from the upstream side in the above-described state, the refrigerant is introduced through the refrigerant passage 263 and a refrigerant passage 265 between the valve portion 241 and the valve seat 233 into the intermediate area 264. Then, the refrigerant is adiabatically expanded as it passes through the restriction 261, and flows downstream through the communication hole 251 a.

At this time, part of the refrigerant introduced into the intermediate area 264 is guided through the through hole 272 and a clearance between the solid shaft 205 and the movable core 204 into the inner space 262. Consequently, the pressure of the refrigerant in the intermediate area 264 and that in the inner space 262 become equal to each other. Further, the pressure of the refrigerant introduced from the upstream side, which is prevailing immediately upstream of the refrigerant passage 265, is held equal to an inlet pressure. Therefore, part of refrigerant pressure applied to the movable core 204 including the non-magnetic member 207 is canceled.

Now, let it be assumed that the pressure of the refrigerant introduced into a refrigerant inlet 221 is represented by P1, the pressure of the refrigerant in the intermediate area 264, which has been reduced due to passage of the refrigerant through the refrigerant passage 265, by P2, the pressure of the refrigerant in a refrigerant outlet 222, which has been further reduced due to passage of the refrigerant through the restriction 261, by P3, the effective pressure-receiving area of the valve portion 241 in a seated state (i.e. the cross-sectional area of the fixed core 203) by A, and the passage cross-sectional area of the restriction 261 by C. Then, a flow rate Gf of the refrigerant flowing through the flow-regulating expansion valve 201 is represented by the following equation: Gf=KC(P2−P3)  (4) where K represents a flow coefficient of the refrigerant.

On the other hand, insofar as the forces acting on the non-magnetic member 207 and hence on the movable core 204 are concerned, assuming that the solenoid force generated by the electric current i is represented by f(i), and the load of the spring 281, which acts in the upstream direction, is represented by fs, the relationship between the forces acting on the non-magnetic member 207 and the movable core 204 in the upstream and downstream directions is represented by the following equation: (A−C) (P2−P3)=fs−f(i)  (5)

From the equations (4) and (5), the flow rate Gf of the refrigerant is represented by the following equation: Gf=(KC/(A−C))(fs−f(i))  (6)

In the right side of the equation (6), the parameters except the solenoid force f(i) are substantially fixed values, and therefore the flow rate Gf is held at a constant value proportional to the electric current i supplied to the solenoid coil 11.

Next, the operation of the flow-regulating expansion valve 201 will be described based on a flow rate characteristic shown in FIG. 6. In FIG. 6, the abscissa represents the value of the electric current i supplied to the solenoid coil 11, and the ordinate represents the flow rate Gf of refrigerant flowing through the flow-regulating expansion valve 201. When the electric current i supplied to the solenoid coil 11 is equal to zero, the valve portion 241 of the movable core 204 is in its open state due to the load fs of the spring 281 to hold the flow-regulating expansion valve 201 in a fully-open state, and hence the flow rate Gf assumes a maximum value determined by the load fs. At this time, when the refrigerant flows, a differential pressure (P2−P3) is generated across the restriction 261.

When the electric current i is supplied to the solenoid coil 11, the movable core 204 is moved in the valve-closing direction to the position where the solenoid force f(i) and the load fs of the spring are balanced with each other, and is stopped there.

At this time, the differential pressure (P2−P3) across the restriction 261 is held at a constant level, based on the principle described in the first embodiment. Consequently, as is apparent from the equation (4), the flow-regulating expansion valve 201 is capable of allowing refrigerant to flow at a constant flow rate dependent on the electric current i supplied to the solenoid coil 11.

Then, when the electric current i exceeds a predetermined value, the flow-regulating expansion valve 201 is fully closed as illustrated in FIG. 4, so as to stop refrigerant from flowing.

As described above, in the flow-regulating expansion valve 201 of the present embodiment as well, substantial integration of the flow-regulating mechanism in the piping of the refrigeration cycle can be achieved, which makes it possible to reduce the size and costs of the flow-regulating expansion valve 201.

It should be noted that although in the present embodiment, the polyimide film 291 is provided to cover the upstream end face of the movable core 204 and the upstream end face of the solid shaft 205 so as to prevent refrigerant within the inner space 262 from flowing out upstream, it is possible to dispense with the sealing member. FIG. 7 shows a variation of the present embodiment.

In the present variation, the axial length of a large-diameter part 253′ of a solid shaft 205′ and that of the upstream end of a movable core 204′ in which the large-diameter part 253′ is inserted are each set to be equal to or larger than a predetermined length to increase the respective axial lengths of sliding surfaces of the two slidably fitted components, whereby leakage of the refrigerant from the inner space 262 in the upstream direction is prevented or suppressed.

[Third Embodiment]

Next, a description will be given of a third embodiment of the present invention. FIG. 8 is a cross-sectional view of a flow-regulating expansion valve of the present embodiment. It should be noted that component elements identical to those in the first embodiment are designated by identical reference numerals on an as-needed basis, and detailed description thereof is omitted.

As shown in FIG. 8, the flow-regulating expansion valve 301 has a pipe 302 in the form of a hollow cylinder, which is a part of the piping of a refrigeration cycle, and accommodates a fixed core 303, a movable core 304, a solid shaft 305, and a hollow cylindrical member 306, with a solenoid section 10 disposed on the outer periphery of the pipe 302 in a manner surrounding the same.

The fixed core 303 has a body in the form of a hollow cylinder having a predetermined inner diameter, and one end of the solid shaft 305 is secured to the upstream end of the fixed core 303 in a suspended manner.

The solid shaft 305 in the form of a stepped cylinder comprises a large-diameter part 351 having an outer diameter substantially equal to the inner diameter of the movable core 304, and a small-diameter part 352 smaller in diameter than the large-diameter part 351. The large-diameter part 351 is located downstream of the fixed core 303, and the small-diameter part 352 extends through the fixed core 303 such that a refrigerant passage is formed. The upstream end of the small-diameter part 352 extends at right angles to the axis of the solid shaft 305, with its extreme end fixed to the fixed core 303.

The movable core 304 has a body in the form of a stepped hollow cylinder in which an upstream part thereof is increased in inner diameter, and is disposed in the pipe 302 at a location downstream of the fixed core 303. The large-diameter part 351 of the solid shaft 305 as a guide for guiding the movable core 304 in the directions of motions thereof is inserted in a large-bore part 341 of the movable core 304. At a location downstream of the large-bore part 341, there is formed a small-bore part 342 smaller in inner diameter than the large-bore part 341, for communication with the downstream side. Further, the movable core 304 has a downstream end formed to have a tapered shape the outer diameter of which progressively decrease toward its downstream extreme end, and the tapered downstream end forms a valve portion 343. Between the movable core 304 and the inner wall of the pipe 302, there is formed a clearance passage 371 which allows passage of refrigerant introduced from the upstream side.

The hollow cylindrical member 306, which is shaped similarly to the fixed core 303, has a fitting groove 361 circumferentially formed in an outer peripheral surface thereof at the center in the axial direction, and the fixing of the hollow cylindrical part 306 in the pipe 302 is attained by swaging a portion of the pipe 302 corresponding to the fitting groove 361 from the outside to thereby fixedly fit the same in the fitting groove 361. The rim of an opening in an upstream end of the hollow cylindrical member 306 forms a valve seat 362 on which the valve portion 343 of the movable core 304 is seated.

Further, a flow-reducing portion 345 in the form of a bottomed hollow cylinder extends downstream from the extreme end of the valve portion 343 of the movable core 304, and a flange 346 projects radially outward from the extreme end of the flow-reducing portion 345. Between the flange 346 and the inner wall of the hollow cylindrical member 306, there is formed a restriction 372. Further, the flow-reducing portion 345 has a side wall thereof formed with a predetermined communication hole 347 for communicating between an intermediate area 373 defined between the flow-reducing portion 345 and the hollow cylindrical member 306, and the small-bore part 342 of the movable core 304.

A spring 381 (elastic member) is interposed between a stepped portion formed at the junction between the large-bore part 341 and the small-bore part 342 and the downstream end face of the solid shaft 304, for urging the movable core 304 downstream, i.e. in the valve-closing direction so as to seat the valve portion 343 on the valve seat 362 to close the valve when the solenoid section 10 is deenergized.

Next, a description will be given of the operation of the flow-regulating expansion valve 301. FIG. 8 shows the flow-regulating expansion valve 301 in the non-energized state of the solenoid coil 11, while FIG. 9 shows the same in the energized state of the solenoid coil 11.

First, in a state of no electric current being supplied to the solenoid coil 11, no attractive force is generated between the movable core 304 and the fixed core 303, and hence, as shown in FIG. 8, the valve portion 343 is seated on the valve seat 362 to hold the flow-regulating expansion valve 301 in a fully-closed state.

Then, when an electric current i is supplied to the solenoid coil 11, a solenoid force the magnitude of which corresponds to the value of the electric current i is generated, whereby the movable core 304 is attracted toward the fixed core 303. As a result, the valve portion 343 of the movable core 304 is held in a position where the solenoid force and the load of the spring 381 are balanced with each other, whereby a predetermined passage cross-section is formed between the valve portion 343 and the valve seat 362.

When a high-pressure refrigerant is introduced from the upstream side in the above-described state, the refrigerant is introduced through a gap between the fixed core 303 and the movable core 304, the clearance passage 371, and the refrigerant passage 374 between the valve portion 343 and the valve seat 362 into the intermediate area 373. Then, the refrigerant is adiabatically expanded due to passage through the restriction 372, and flows downstream.

At this time, part of the refrigerant introduced into the intermediate area 373 is also introduced through the communication hole 347 and the small-bore part 342 into an inner space 375 formed between the movable core 304 and the solid shaft 305. Consequently, the pressure of the refrigerant in the intermediate area 373 and that in the inner space 375 become equal to each other, and hence part of refrigerant pressure applied to the movable core 304 is canceled.

Now, let it be assumed that the pressure of the refrigerant introduced into a refrigerant inlet 321 is represented by P1, the pressure of the refrigerant in the intermediate area 373, which has reduced due to passage of the refrigerant through the refrigerant passage 374, by P2, the pressure of the refrigerant in a refrigerant outlet 322, which has further reduced due to passage of the refrigerant through the restriction 372, by P3, the effective pressure-receiving area of the valve portion 343 in a seated state (i.e. the cross-sectional area of the hollow cylindrical member 306) by A, and the passage cross-sectional area of the restriction 372 by C. Then, a flow rate Gf of the refrigerant flowing through the flow-regulating expansion valve 301 is represented by the following equation: Gf=KC(P2−P3)  (7)

-   -   where K represents a flow coefficient of the refrigerant.

On the other hand, insofar as the forces acting on the movable core 304 are concerned, assuming that the solenoid force generated by the electric current i is represented by f(i), and the load of the spring 381, which acts in the upstream direction, is represented by fs, the relationship between the forces acting on the movable core 304 in the upstream and downstream directions is represented by the following equation: (A−C)(P2−P3)=f(i)fs  (8)

From the equations (7) and (8), the flow rate Gf of the refrigerant is represented by the following equation: Gf=(KC/(A−C))(f(i)fs)  (9)

In the right side of the equation (9), the parameters except the solenoid force f(i) are substantially fixed values, and therefore the flow rate Gf is held at a constant value proportional to the electric current i supplied to the solenoid coil 11.

[Fourth Embodiment]

Next, a description will be given of a fourth embodiment of the present invention. FIG. 10 is a cross-sectional view of a flow-regulating expansion valve of the present embodiment. It should be noted that component elements identical to those in the above-described embodiments are designated by identical reference numerals on an as-needed basis, and detailed description thereof is omitted.

As shown in FIG. 10, the flow-regulating expansion valve 401 has a pipe 202 in the form of a hollow cylinder accommodating a fixed core 403, a movable core 404, and a solid shaft 405, with a solenoid section 10 disposed on the outer periphery of the pipe 202 in a manner surrounding the same.

The fixed core 403 has a body in the form of a hollow cylinder and is press-fitted in the pipe 202. The rim of an opening in a downstream end of the fixed core 403 forms a valve seat 431, and a flange 432 is formed at an axially intermediate portion thereof in a manner protruding radially inward.

The movable core 404 has a body in the form of a stepped hollow cylinder the inner diameter of which is increased at a downstream end thereof, and is disposed in the pipe 202 at a location downstream of the fixed core 403. The movable core 404 has an upstream end thereof formed to have a tapered shape the outer diameter of which progressively decreases upstream, and the tapered upstream end forms a valve portion 441 which can be seated on the valve seat 431. The movable core 404 has a small-bore part 442 and a large-bore part 443 downstream of the small-bore part 442, and the solid shaft 405 is inserted in the large-bore part 443. Between the movable core 404 and the inner wall of the pipe 202, there is formed a clearance passage 461 which allows passage of refrigerant introduced from the upstream side.

Further, a pressure-equalizing pipe 409 in the form of a hollow cylinder is fitted into the end of the valve portion 441 of the movable core 404, and extends into the fixed core 403. The extreme end of the pressure-equalizing pipe 409 reaches a location slightly upstream of the flange 432 to form a restriction 462 between the flange 432 and the pressure-equalizing pipe 409. A spring 481 (elastic member) is interposed between the flange 432 and the upstream end face of the movable core 404, with the opposite ends thereof fixed to the fixed core 403 and the movable core 404, respectively, such that the movable core 404 is supported by the fixed core 403 with a predetermined space therebetween when the solenoid section 10 is deenergized.

The solid shaft 405 is in the form of a stepped column, and a large-diameter part 451 thereof is fitted in the large-bore part 443 of the movable core 404 to guide the movable core 404 in the directions of motions thereof. A small-diameter part 452 is downstream of the large-diameter part 451 in a manner continuous therewith, and the lower end thereof is fixed to a disk-shaped stopper 407 rigidly press-fitted in the pipe 202. The stopper 407 has a communication hole 471 axially formed therethrough to form a part of a refrigerant passage through the flow-regulating expansion valve 401. Between a stepped portion formed at the junction of the large-bore part 443 of the movable core 404 and the small-bore part 442 of the same and the upstream end face of the solid shaft 405, there is formed an inner space 463 communicating with the refrigerant passage via the small-bore part 442 and the pressure-equalizing pipe 409. The cross-sectional area of the inner space 463 is set to be equal to that of the lower end of an intermediate area 464, referred to hereinafter.

Next, a description will be given of the operation of the flow-regulating expansion valve 401. FIG. 11 shows the open state of the flow-regulating expansion valve 401, while FIG. 10 shows the fully-closed state of the same.

First, in a state of no electric current being supplied to the solenoid coil 11, no attractive force is generated between the movable core 404, which is supported by the spring 481, and the fixed core 403, and hence, as shown in FIG. 11, the valve portion 441 is held away from the valve seat 431 to hold the flow-regulating expansion valve 401 in its open state.

Then, when an electric current i is supplied to the solenoid coil 11, a solenoid force the magnitude of which corresponds to the value of the electric current i is generated, whereby the movable core 404 is attracted toward the fixed core 403. As a result, a force acting in the direction of seating the valve portion 441 of the movable core 404 against the urging force of the spring 481 is generated. Consequently, the valve portion 441 is held in a position where the solenoid force and the load of the spring 481 are balanced with each other, whereby a predetermined passage cross-section is formed between the valve portion 441 and the valve seat 431.

When a high-pressure refrigerant is introduced from the upstream side in the above-described state, the refrigerant is adiabatically expanded due to passage through the restriction 462 and then introduced into the intermediate area 464. Further, the refrigerant passes through a refrigerant passage 465 between the valve portion 441 and the valve seat 431, and the clearance passage 461, and flows downstream through the communication hole 471.

At this time, the pressure of the refrigerant in the inner space 463 is equal to an inlet pressure via the pressure-equalizing pipe 409, and hence part of refrigerant pressure applied to the movable core 404 including the pressure-equalizing pipe 409 is canceled.

Now, let it be assumed that the pressure of the refrigerant introduced into a refrigerant inlet 421 is represented by P1, the pressure of the refrigerant in the intermediate area 464, which has been reduced due to passage through the restriction 462, by P2, the pressure of the refrigerant in a refrigerant outlet 422, which has been further reduced due to passage through the refrigerant passage 465, by P3, the effective pressure-receiving area of the valve portion 441 in a seated state (i.e. the cross-sectional area of the lower end of the intermediate area 464, which is equal to that of the inner space 463) by A, the cross-sectional area of a circle having the outer diameter of the pressure-equalizing pipe 409 by B, and the passage cross-section of the restriction 462 by C. Then, a flow rate Gf of the refrigerant flowing through the flow-regulating expansion valve 401 is represented by the following equation: Gf=KC(P1−P2)  (10)

-   -   where K represents a flow coefficient of the refrigerant.

On the other hand, insofar as the forces acting on the movable core 404 are concerned, assuming that the solenoid force generated by the electric current i is represented by f(i), and the load of the spring 481, which acts in the upstream direction, is represented by fs, the relationship between the forces acting on the movable core 404 in the upstream and downstream directions is represented by the following equation: (A−B)(P1−P2)=fs−f(i)  (11)

From the equations (10) and (11), the flow rate Gf of the refrigerant is represented by the following equation: Gf=(KC/(A−B))(fs−f(i))  (12)

In the right side of the equation (12), the parameters except the solenoid force f(i) are substantially fixed values, and therefore the flow rate Gf is held at a constant value proportional to the electric current i supplied to the solenoid coil 11.

It should be noted that although in the present embodiment, the pressure-equalizing pipe 409 for communicating with the inner space is provided in a manner extending from the movable core 404 such that the restriction 462 is formed between the pressure-equalizing pipe 409 and the flange 432 of the fixed core 403, a variation shown in FIG. 12 can also be employed.

In a flow-regulating expansion valve 401′ of the variation, a passage pipe 409′ extending into the inner space 463 of the movable core 404′ is rigidly fitted in the flange 432 of the fixed core 403, and a restriction 462′ is formed between the passage pipe 409′ and the inner wall of a small-bore part 442′ of the movable core 404′.

In this case, when a high-pressure refrigerant is introduced from the upstream side in the open state of the valve portion 441, the refrigerant is adiabatically expanded due to passage through the restriction 462′ via the inner space 463. Then, the refrigerant passes through the refrigerant passage 465 between the valve portion 441 and the valve seat 431, and the clearance passage 461, and flows downstream through the communication hole 471.

[Fifth Embodiment]

Next, a description will be given of a fifth embodiment of the present invention. FIG. 13 is a cross-sectional view of a flow-regulating expansion valve of the present embodiment. It should be noted that component elements identical to those in the above-described embodiments are designated by identical reference numerals on an as-needed basis, and detailed description thereof is omitted.

As shown in FIG. 13, the flow-regulating expansion valve 501 has a pipe 202 in the form of a hollow cylinder accommodating a fixed core 503, a movable core 504, and a solid shaft 505, with a solenoid section 10 disposed on the outer periphery of the pipe 202 in a manner surrounding the same.

The fixed core 503 has a body in the form of a hollow cylinder and is press-fitted in the pipe 202. The rim of an opening in an upstream end of the fixed core 503 forms a valve seat 531, and the inner diameter thereof is slightly reduced at a location axially downstream of the valve seat 531 to form a stepped portion 532. The stepped portion 532 has a disk-shaped stopper 507 rigidly press-fitted therein. The stopper 507 has a communication hole 571 axially formed therethrough to form a part of a refrigerant passage through the flow-regulating expansion valve 501.

The movable core 504 has a body in the form of a stepped hollow cylinder the inner diameter of which is increased at an upstream end thereof, and is disposed in the pipe 202 at a location upstream of the fixed core 503. The movable core 504 has a downstream end thereof formed to have a tapered shape the outer diameter of which progressively decreases downstream, and the tapered downstream end forms a valve portion 541 which can be seated on the valve seat 531. The movable core 504 has a large-bore part 542 and a small-bore part 543 downstream of the large-bore part 542, through which the solid shaft 505 extends. A restriction 561 is formed between the movable core 504 and the inner wall of the pipe 202.

Further, the movable core 504 has a flat face orthogonal to the axis, formed at a downstream extreme end thereof, and a spring 581 (elastic member) is interposed between the flat face and the upstream end face of the stopper 507 such that the movable core 504 is supported by the fixed core 503 with a predetermined space therebetween when the solenoid section 10 is deenergized.

The solid shaft 505 is in the form of a stepped column, and the lower end of a small-diameter part 552 thereof is fixed to the upstream end face of the stopper 507. The small-diameter part 552 has the movable core 504 fitted thereon to guide the same in the directions of motions thereof. Further, a large-diameter part 551 formed in the upstream end of the solid shaft 505 not only guides the large-bore part of the movable core 504, but also defines a predetermined inner space 562 between a stepped portion formed at the junction between the small-diameter part 552 and the large-diameter part 551 of the solid shaft 505 and the movable core 504.

Further, a polyimide film 291 is provided on the upstream end face of the movable core 504 and the upstream end face of the solid shaft 505 in a manner hermetically covering these.

Next, a description will be given of the operation of the flow-regulating expansion valve 501. FIG. 13 shows the open state of the flow-regulating expansion valve 501, while FIG. 14 shows the fully-closed state of the same.

First, in a state of no electric current being supplied to the solenoid coil 11, no attractive force is generated between the movable core 504, which is supported by the spring 581, and the fixed core 503, and hence, as shown in FIG. 13, the valve portion 541 is held away from the valve seat 531 to hold the flow-regulating expansion valve 501 in its open state.

Then, when an electric current i is supplied to the solenoid coil 11, a solenoid force the magnitude of which corresponds to the value of the electric current i is generated, whereby the movable core 504 is attracted toward the fixed core 503. As a result, a force acting in the direction of seating the valve portion 541 of the movable core 504 against the urging force of the spring 581 is generated. Consequently, the valve portion 541 is held in a position where the solenoid force and the load of the spring 581 are balanced with each other, whereby a predetermined passage cross-section is formed between the valve portion 541 and the valve seat 531.

When a high-pressure refrigerant is introduced from the upstream side in the above-described state, the refrigerant is adiabatically expanded due to passage through the restriction 561 and then introduced into an intermediate area 564. Further, the refrigerant flows downstream via a refrigerant passage 565 between the valve portion 541 and the valve seat 531, and the communication hole 571.

At this time, part of the refrigerant passing through the intermediate area 564 is introduced through a clearance between the small-diameter part 552 and the movable core 504 into the inner space 562. Consequently, an outlet pressure at a location downstream of the intermediate area 564 and the pressure of the refrigerant in the inner space 562 become equal to each other. Therefore, part of refrigerant pressure applied to the movable core 504 is canceled.

Now, let it be assumed that the pressure of the refrigerant introduced into a refrigerant inlet 521 is represented by P1, the pressure of the refrigerant in the intermediate area 564, which has been reduced due to passage of the refrigerant through the restriction 561, by P2, the pressure of the refrigerant in a refrigerant outlet 522, which has been further reduced due to passage of the refrigerant through the refrigerant passage 565, by P3, the effective pressure-receiving area of the valve portion 541 in a seated state (i.e. the cross-sectional area of the inner space 562) by A, the area of the circle having the outer diameter of the upstream end face of the movable core 504 by B, and the passage cross-sectional area of the restriction 561 by C. Then, a flow rate Gf of the refrigerant flowing through the flow-regulating expansion valve 501 is represented by the following equation: Gf=KC(P1−P2)  (13)

-   -   where K represents a flow coefficient of the refrigerant.

On the other hand, insofar as the forces acting on the movable core 504 are concerned, assuming that the solenoid force generated by the electric current i is represented by f(i), and the load of the spring 581, which acts in the upstream direction, is represented by fs, the relationship between the forces acting on the movable core 504 in the upstream and downstream directions is represented by the following equation: (B−A)(P1−P2)=fs−f(i)  (14)

From the equations (13) and (14), the flow rate Gf of the refrigerant is represented by the following equation: Gf=(KC/(B−A))(fs−f(i))  (15)

In the right side of the equation (15), the parameters except the solenoid force f(i) are substantially fixed values, and therefore the flow rate Gf is held at a constant value proportional to the electric current i supplied to the solenoid coil 11.

Then, when the electric current i exceeds a predetermined value, the flow-regulating expansion valve 501 is fully closed as illustrated in FIG. 14, so as to stop refrigerant from flowing.

[Sixth Embodiment]

Next, a description will be given of a sixth embodiment of the present invention. FIG. 15 is a cross-sectional view of a flow-regulating expansion valve of the present embodiment. It should be noted that component elements identical to those in the above-described embodiments are designated by identical reference numerals on an as-needed basis, and detailed description thereof is omitted.

As shown in FIG. 15, the flow-regulating expansion valve 601 has a pipe 202 in the form of a hollow cylinder accommodating a fixed core 603, a movable core 604, and a hollow cylindrical member 605, with a solenoid section 10 disposed on the outer periphery of the pipe 202 in a manner surrounding the same.

The fixed core 603 has a body in the form of a bottomed hollow cylinder having a bottom at its upstream end, and is press-fitted in the pipe 202. The fixed core 603 has a circular recess 631 formed at the upstream end, for accommodating a part of a spring 681, referred to hereinafter, and a valve seat 632 is integrally formed with the rim of an opening of the recess 631, in a manner protruding upstream therefrom. Further, a communication hole 634 is formed through a portion of the side wall of the upstream end of the fixed core 603, for communicating between an internal refrigerant passage 633 and the upstream side.

The movable core 604 has a body in the form of a stepped hollow cylinder which has a stepped portion at its downstream end, and is disposed in the pipe 202 at a location upstream of the fixed core 603. The movable core 604 has a large-bore part thereof slidably fitted on a hollow cylindrical shaft part extending downstream from the hollow cylindrical member 605 fixed in the pipe 202 at a location further upstream of the movable core 604. In the center of the stepped portion of the movable core 604, i.e. the bottom of the large-bore part, there is formed a circular restriction 643. The downstream end face of the movable core 604 in which the restriction 643 opens has a flat portion formed for allowing the spring 681 to be brought into contact therewith, and a tapered portion the diameter of which progressively increases downstream from the flat portion. The surface of the tapered portion forms a valve portion 641 which can be seated on the valve seat 632.

The spring 681 (elastic member) is interposed between the downstream end face of the movable core 604 and the recess 631 of the fixed core 603. When the solenoid section 10 is not energized, the movable core 604 is supported by the fixed core 603 with a predetermined space therebetween. Between the movable core 604 and the pipe 202, there is formed a predetermined clearance 661.

Next, a description will be given of the operation of the flow-regulating expansion valve 601. FIG. 15 shows the open state of the flow-regulating expansion valve 601, while FIG. 16 shows the fully-closed state of the same.

First, in a state of no electric current being supplied to the solenoid coil 11, no attractive force is generated between the movable core 604, which is supported by the spring 681, and the fixed core 603, and hence, as shown in FIG. 16, the valve portion 641 is held away from the valve seat 632 to hold the flow-regulating expansion valve 601 in its fully-open state.

Then, when an electric current i is supplied to the solenoid coil 11, a solenoid force the magnitude of which corresponds to the value of the electric current i is generated, whereby the movable core 604 is attracted toward the fixed core 603. As a result, a force acting in the direction of seating the valve portion 641 of the movable core 604 against the urging force of the spring 681 is generated. Consequently, the valve portion 641 is held in a position where the solenoid force and the load of the spring 681 are balanced with each other, whereby a predetermined passage cross-section is formed between the valve portion 641 and the valve seat 632.

When a high-pressure refrigerant is introduced from the upstream side in the above-described state, the refrigerant is adiabatically expanded due to passage through the restriction 643 and then introduced into an intermediate area 664 between the downstream end face of the movable core 604 and the recess 631 of the fixed core 603. Further, the refrigerant flows downstream via a refrigerant passage 665 between the valve portion 641 and the valve seat 632, the communication hole 634, and the internal refrigerant passage 633.

At this time, part of the refrigerant passing through the intermediate area 664 is introduced through the clearance 661 into an inner space 662 defined between the hollow cylindrical member 605 and the upstream end face of the movable core 604. Consequently, part of refrigerant pressure applied to the movable core 604 is canceled.

Now, let it be assumed that the pressure of the refrigerant introduced into a refrigerant inlet 621 is represented by P1, the pressure of the refrigerant in the intermediate area 664, which has been reduced due to passage of the refrigerant through the restriction 643, by P2, the pressure of the refrigerant in a refrigerant outlet 622, which has been further reduced due to passage of the refrigerant through the refrigerant passage 665, by P3, the effective pressure-receiving area of the valve portion 641 in a seated state (i.e. the cross-sectional area of the movable core 604) by A, and the passage cross-sectional area of the restriction 643 by C. Then, a flow rate Gf of the refrigerant flowing through the flow-regulating expansion valve 601 is represented by the following equation: Gf=KC(P1−P2)  (16)

-   -   where K represents a flow coefficient of the refrigerant.

On the other hand, insofar as the forces acting on the movable core 604 are concerned, assuming that the solenoid force generated by the electric current i is represented by f(i), and the load of the spring 681, which acts in the upstream direction, is represented by fs, the relationship between the forces acting on the movable core 604 in the upstream and downstream directions is represented by the following equation: (A−C)(P1−P2)=fs−f(i)  (17)

From the equations (16) and (17), the flow rate Gf of the refrigerant is represented by the following equation: Gf=(KC/(A−C))(fs−f(i))  (18)

In the right side of the equation (18), the parameters except the solenoid force f(i) are substantially fixed values, and therefore the flow rate Gf is held at a constant value proportional to the electric current i supplied to the solenoid coil 11.

Then, when the electric current i exceeds a predetermined value, the flow-regulating expansion valve 601 is fully closed as illustrated in FIG. 16, so as to stop refrigerant from flowing.

Although the preferred embodiments of the present invention have been described heretofore, the present invention is by no means limited to any specific one of the above-described embodiments, but various modifications and alterations can be made thereto without departing the spirit and scope of the present invention.

The present invention is applicable to a flow-regulating expansion valve provided in a flow passage of refrigerant circulating through a refrigeration cycle, for decompressing refrigerant flowing in from an upstream side by adiabatically expanding the refrigerant, and delivering the refrigerant at a predetermined constant flow rate.

According to the flow-regulating expansion valve of the present invention, the pipe accommodating the internal structures serves as a part of the refrigerant passage of the refrigeration cycle. Further, the solenoid coil is disposed outside the pipe in a manner surrounding the same. Therefore, substantial integration of the flow-regulating mechanism in the piping of the refrigeration cycle can be achieved, which makes the entire flow-regulating expansion valve 1 very simple in construction.

Further, differently from the prior art in which an area for installation of a solenoid coil is separately provided, the flow-regulating expansion valve is thus integrated in the piping of the refrigeration cycle, which enables reduction of an area occupied by the flow-regulating expansion valve in the refrigeration cycle.

As a result, reduction of the size of the flow-regulating expansion valve and resultant reduction of material costs and manufacturing costs can be achieved, which makes it possible to achieve low costs of the flow-regulating expansion valve.

The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents. 

1. A flow-regulating expansion valve provided in a flow passage of refrigerant circulating through a refrigeration cycle, for decompressing refrigerant flowing in from an upstream side thereof by adiabatically expanding the refrigerant, and delivering the refrigerant at a constant flow rate set by a value of an electric current supplied to a solenoid coil, the flow-regulating expansion valve comprising: a pipe forming a part of the refrigerant flow passage; a fixed core in the form of a hollow cylinder fixed in the pipe; a movable core in the form of a hollow cylinder disposed in the pipe in a manner opposed to the fixed core in an axial direction such that the movable core is movable in the axial direction; the solenoid coil circumferentially disposed outside the pipe in a manner surrounding the pipe, for generating a magnetic circuit including the movable core and the fixed core by an electric current which is externally supplied, to generate a solenoid force a magnitude of which corresponds to a value of the supplied electric current to thereby move the movable core to a predetermined reference position with respect to the fixed core; and a flow-regulating mechanism provided in the pipe, for performing valve-opening or valve-closing operation while moving the movable core to and from the predetermined reference position to adjust an internal passage cross-section, and delivering the refrigerant downstream at the constant flow rate.
 2. The flow-regulating expansion valve according to claim 1, wherein the flow-regulating mechanism comprises: a restriction formed by a fixed passage having a predetermined passage cross-section; a valve seat provided in the pipe; and a valve element formed such that the valve element can be removably seated on the valve seat by motion of the movable core, the valve element allowing the refrigerant to flow downstream through a gap between the valve element and the valve seat when the valve element is open, and wherein a passage cross-section formed between the valve element and the valve seat is adjusted by the motion of the movable core such that a differential pressure across the restriction is held constant, whereby the flow rate of the refrigerant flowing downstream is held constant.
 3. The flow-regulating expansion valve according to claim 2, comprising a hollow member having one end-side part thereof fixedly fitted in the movable core and an opposite end-side part thereof slidably inserted in the fixed core, a part of the opposite end-side part being reduced in inner diameter to form the restriction, and a plurality of support portions formed at circumferentially spaced intervals in a manner extending from an extreme end of the opposite end-side part, and wherein the valve seat is formed on an end of the fixed core opposite from the movable core, and wherein the valve element has a guide portion in the form of a hollow cylinder guided by a hollow shaft in the form of a bottomed hollow cylinder provided on a side of the fixed core opposite from the movable core, and a valve portion configured such that the valve portion can be seated on the valve seat, the valve portion being formed with a communication hole for communicating between an inside of the guide portion and an inside of the hollow shaft, the valve element being urged toward the fixed core by a elastic member provided within the hollow shaft, and wherein energization of the solenoid coil causes the hollow member to urge the valve element via the support portions to thereby move the valve element away from the valve seat such that the passage cross-section is formed between the valve element and the valve seat.
 4. The flow-regulating expansion valve according to claim 2, comprising a solid shaft in the form of a stepped column, the solid shaft having the movable core fitted on one end-side part thereof formed with a stepped portion to guide the movable core in directions of motion thereof, an opposite-end side part of the solid shaft being fixed in the pipe, and a sealing member mounted on an end face of the movable core opposite from the fixed core and a one end-side end face of the solid shaft in a manner hermetically covering the end faces, and wherein the valve seat is formed on a movable core-side end of the fixed core, and wherein the movable core has a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, and a non-magnetic member in the form of a hollow cylinder formed in a manner continuous with the body and extending therefrom into the fixed core, the non-magnetic member being circumferentially formed with a flange for forming the restriction between an inner wall of the fixed core and the flange, and forms a predetermined inner space between the stepped portion of the solid shaft and the movable core itself.
 5. The flow-regulating expansion valve according to claim 2, comprising a solid shaft in the form of a stepped column, the solid shaft having the movable core fitted on one end-side part thereof formed with a stepped portion to guide the movable core in directions of motion thereof, an opposite-end side part of the solid shaft being fixed in the pipe, and wherein the valve seat is formed on a movable core-side end of the fixed core, and wherein the movable core has a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, and a non-magnetic member in the form of a hollow cylinder formed in a manner continuous with the body and extending therefrom into the fixed core, the non-magnetic member being circumferentially formed with a flange for forming the restriction between an inner wall of the fixed core and the flange, and forms a predetermined inner space between the stepped portion of the solid shaft and the movable core itself, and wherein sliding surfaces of the solid shaft and the movable core, which communicate with the inner space, on a side opposite from the fixed core, are configured to have a length not shorter than a predetermined length such that leakage of the refrigerant via the sliding surfaces can be suppressed.
 6. The flow-regulating expansion valve according to claim 2, comprising a solid shaft in the form of a column, the solid shaft having the movable core fitted on one end-side part thereof to guide the movable core in directions of motion thereof, an opposite-end side part of the solid shaft being fixed in the pipe, and wherein the movable core has a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, and forming a predetermined clearance passage axially extending between the pipe and the movable core itself, and a flow-reducing portion formed continuous with the valve portion, and having a flange formed thereon in a protruding manner to form the restriction between an inner wall of the pipe or a hollow cylindrical member fitted in the pipe, the movable core further forming, between the solid shaft and the movable core itself, a predetermined inner space for communicating with the refrigerant flow passage.
 7. The flow-regulating expansion valve according to claim 6, wherein the fixed core, the movable core, and the hollow cylindrical member having the valve seat fixed in the pipe are arranged in the mentioned order from an upstream side of the refrigerant flow passage, and wherein an upstream end of the solid shaft extends through the fixed core while maintaining a refrigerant passage, with an extreme upstream end of the solid shaft fixed on an upstream end of the fixed core, and wherein an elastic member is interposed between a downstream end of the solid shaft and an inner wall of the movable core, for connecting between the solid shaft and the movable core to support the movable core.
 8. The flow-regulating expansion valve according to claim 2, comprising a solid shaft in the form of a column, the solid shaft having the movable core fitted on one end-side part thereof to guide the movable core in directions of motion thereof, an opposite-end side part of the solid shaft being fixed in the pipe, and wherein the fixed core has the valve seat formed on a movable core-side end thereof, with a flange formed thereon in a manner protruding inward at a predetermined axial location, and wherein the movable core comprises: a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, and forming a predetermined clearance passage axially extending between the pipe and the movable core itself, the movable core further forming, between the solid shaft and the movable core itself, a predetermined inner space for communicating with the refrigerant flow passage; and a pressure-equalizing pipe fitted in the body in a manner extending into the fixed core and communicating with the inner space, and wherein the restriction is formed between an end of the pressure-equalizing pipe and the flange part.
 9. The flow-regulating expansion valve according to claim 2, comprising a solid shaft in the form of a column, the solid shaft having the movable core fitted on one end-side part thereof to guide the movable core in directions of motion thereof, an opposite-end side part of the solid shaft being fixed in the pipe, and wherein the fixed core has the valve seat formed on a movable core-side end thereof, and further the fixed core has a flange formed thereon in a manner protruding inward at a predetermined axial location, and a passage pipe extending into the movable core, and wherein the movable core has a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, and forming a predetermined clearance passage axially extending between the pipe and the movable core itself, the movable core further forming, between the solid shaft and the movable core itself, a predetermined inner space for communicating with the refrigerant flow passage, and wherein the restriction is formed between the passage pipe and the movable core.
 10. The flow-regulating expansion valve according to claim 2, comprising a solid shaft in the form of a stepped column, the solid shaft having the movable core fitted on one end-side part thereof formed with a stepped portion to guide the movable core in directions of motion thereof, an opposite-end side part of the solid shaft being fixed in the fixed core, and a sealing member mounted on an end face of the movable core opposite from the fixed core and a one end-side end face of the solid shaft in a manner hermetically covering the end faces, and wherein the valve seat is formed on a movable core-side end of the fixed core, and wherein the movable core has a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, and forms a predetermined inner space between the solid shaft and the movable core itself, and a predetermined clearance axially extending between the pipe and the movable core itself, the restriction being formed by the clearance.
 11. The flow-regulating expansion valve according to claim 2, wherein the valve seat is formed on a movable core-side end of the fixed core, and wherein the movable core has a body in the form of a hollow cylinder having a valve portion of the valve element formed at an extreme end thereof such that the valve portion can be seated on the valve seat, with a portion thereof in the vicinity of the valve portion being reduced in inner diameter to form the restriction, and a large-bore part thereof formed on a side of the restriction opposite from the fixed core being fitted on a hollow cylindrical member rigidly fitted in the pipe, such that the movable core is guided by the hollow cylindrical member. 